SCIENCE- G OS SIP. 



8s 



PHOTOGRAPHY FOR BEGINNERS. 

 By B. Foulkes- Winks, M.R.P.S. 



( Continued from page. 53.) 



Section I. Cameras {continued). 



Twin-lens Cameras. — As the best representa- 

 tive of this class of hand-camera we take the 

 " Ross Twin-lens," manufactured by Messrs. Ross, 

 Limited. As will be seen by the illustration 

 (fig. 1), this is of the box-form, and is fitted with 



Fig. 1. "Ross" Twin-Lens Camera, closed. 



two lenses of identical focus. The top lens is used 

 for focussing the view by means of a hood which 

 is shown raised ready for use in fig. 2. The picture 

 is composed and focussed on the ground glass 



Fig. 2. " Ross " Twin-Lens Camera, open. 



fitted to the top of the camera. The image is 

 thrown on to the ground glass by means of a 

 mirror placed at an angle of 45° at the back of 

 the focussing lens. Both lenses are racked in or 

 out, as the case may require, simultaneously. The 



second, or lower, lens is used for taking the picture, 

 and is therefore fitted with an instantaneous 

 shutter, both lenses being "paired" — that is, of 

 absolutely the same focus, and so adjusted upon 

 one front-board as to represent the same view 

 in every respect ; one on the ground glass focussing 

 screen, and the other upon the sensitive plate. The 

 rack-work focusses both lenses at the same time ; 

 so it will be obvious that whatever object is 

 seen on the ground glass will also appear on the 

 negative with the same degree of sharpness and 

 proportion. 



There are many makes of twin-lens cameras on 

 the market, some of which are fitted with changing 

 apparatus of various forms, but the one which we 

 have taken as descriptive of this type of camera is 

 fitted either with dark slides or a changing-box, 

 both of which can be carried separately, and so 

 lessen the weight of the camera. It is needless to 

 say that the camera is beautifully made and 

 finished, emanating as it does from such a well- 

 known firm as Messrs. Ross, Limited, who are 

 celebrated all over the world for their various 

 manufactures. These cameras may be fitted 

 with " Ross " rapid hand-camera lenses working 

 at 5"6, "Zeiss" lenses, " Goerz " anastigmats, or, 

 in fact, any lenses that are capable of being 

 paired. 



We have seen some very good cameras of the 

 twin-lens type made by Messrs. Lizars, of Glas- 

 gow ; Messrs. Perken, Son & Co., of Hatton Garden, 

 E.C. ; Messrs. W. Butcher & Son, Blackheath, S.E. ; 

 also by the London Stereoscopic and Photographic 

 Co., Regent Street, W. The fact of these cameras 

 being constructed to carry two lenses, with separate 

 focussing and exposing chambers, necessitates 

 their being somewhat bulky and heavy as com- 

 pared with the ordinary single-lens hand-cameras. 

 This drawback, however, is more than compensated 

 for by the enormous advantage of being able to see 

 a facsimile of the picture whilst being taken, even 

 during the time of exposure. This is of particular 

 value where the camera is being used for por- 

 traiture, etc. 



In selecting a hand-camera of the twin-lens type 

 it will be found that they are generally supplied with 

 dark slides. We should strongly advise the pur- 

 chaser to select one with a changing-box attached, 

 as it will be found in practice that dark slides are 

 much too slow in changing for hand-camera work. 

 It often happens that the photographer desires 

 to make two or three exposures in rapid succes- 

 sion, and we would also lay stress upon the 

 advisability of procuring the best lenses con- 

 sistently with the amount of money it is proposed 

 to spend. Mention also should be made of the 

 instantaneous shutter, which it is desirable should 

 be one that does not open in setting- when a 

 changing-box is used, although this is of little 

 consequence when dark slides are employed. In 

 the event of a focal plane shutter being fixed to 

 one of these cameras, it will be necessary to devise 

 some means of covering up the lens while the 

 shutter is being set. There are, however, two 

 objections lodged against this type of camera by 

 certain workers — one is the expense entailed by 

 the necessity of having two lenses, and the other is 

 that the camera is constructed for taking pictures 

 only the horizontal way of the plate ; but this 

 latter objection may be remedied to an extent by 

 using a finder for taking vertical pictures. 



{To oe continued.') 



